1. Field of the Invention
The present invention relates to an apparatus for separating different constituents of a multifraction product by means of a dense liquid medium. As a result of settling due to differences in specific gravity, a light fraction floats on the dense medium, middlings fraction remains suspended in the dense medium, and a higher density fraction sinks to the bottom of the medium. The invention is particularly concerned with the removal of the dense fraction from the liquid medium without contamination by the other fractions.
2. Description of the Prior Art
The separation of different constituents by means of settling in a dense liquid is known in various embodiments in the prior art. In particular, the application of such methods is widespread in mining for processing coal and ore. The method has also been recently applied for recycling various materials such as metals. The recycling of valuable metals from scrap, particularly from automotive scrap, is a preferred field of application for this type of method.
In a conventional method of this sort, the product is normally delivered onto the dense liquid medium, a floating fraction is extracted from the dense medium and the heavy fraction sinks to the bottom under the force of gravity. Since the dense fraction sinks essentially perpendicularly, the removal of the heavy fraction must essentially begin in those regions of the dense liquid medium in which the floating light fraction covers the surface of the medium. With conventional withdrawal, therefore, a certain portion of suspended product (middlings) and the low density floating product is necessarily withdrawn together with the heavier fraction. Thus, the separated heavy fraction is contaminated with constituents of the suspended product and of the lower density floating material so that an insufficient separation is achieved.